Adjustable constant current ionization device



Sept. 7, 1965 J. F. GRIMM ETAL 3,205,389

ADJUSTABLE CONSTANT CURRENT IONIZATION DEVICE Filed Jan. 21, 1963 m4 200 v. I I

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BY Mae/r-vs A. SAM/was m M K C M ATTORNEYS United States Patent ()fi ice 3,205,389 Patented Sept. 7, 1965 3,205,389 ADJUSTABLE C(BNSTANT CURRENT IONIZATIUN DEVICE John F. Grimm, Newark, and Anthony Scala, Livingston, N.J., and Morris H. Shamos, River-dale, J.Y., assignors to Tong-Sol Electric Inc., a corporation of Delaware Filed Jan. 21, 1963, Set. No. 252,871 Claims. (Cl. 313-54) This invention relates to a diode containing means for ionizing a gas and adapted to pass a constant current of small and adjustable magnitude. The invention has particular reference to a means for adjusting the constant current over a wide range of values by means of a manually controlled shield.

It has been known for some time that ionization devices enclosed within an envelope and containing gas at a reduced pressure can be used as circuit components for the passage of a constant current over a wide range of applied voltages. These components have been called Curpistors and will pass constant current within the voltage range of to 1000 volts, the upper limit depending upon the gas and pressure. Below 15 volts the devices are linear and above 1000 volts they generally break down into a glow discharge. So far as it is known none of these devices have ever been made with a wide range of adjustable resistances and the present invention fills this need by the use of an internal shield which is controlled by screw means external of the envelope and which employs a serrated edge to produce a gradual controlled current characteristic.

One of the objects of this invention is to provide an improved adjustable constant current device which avoids one or more of the disadvantages and limitations of prior art arrangements.

Another object of the invention is to provide an ad justable constant current device for electronic circuits passing currents within the range of 10 to 10- amperes.

Another object of the invention is to provide a calibrated adjustment for constant current devices which enables an operator to adjust quickly for a desired current value.

Another object of the invention is to shield a constant current device so that it is not affected by external electric fields.

Another object of the invention is to provide a visual indication on the external portion of the device which indicates the constant current value.

Another object of the invention is to provide a gradual variation of current values by means of a shield so that the motion of the shield is proportional to the square of the current.

The invention includes an adjustable current device comprising an envelope containing an ionized gas, an anode, a plurality of areas carrying radio-active material for ionizing the gas, and a movable shield for shielding portions of the areas to vary the amount of gas ionization. A feature of the invention includes a serrated edge on the shield for providing a gradual increase in ionization as the shield is moved. Another feature of the invention includes a mechanical means external of the envelope for manually controlling the movement of the shield.

For a better understanding of the present invention together with other and further objects thereof, reference is made to the following description taken in connection with the accompanying drawings.

FIG. 1 is a view of the constant current device showing the calibration lines which are used for calibrating the instrument.

FIG. 2 is a cross sectional view taken along the center line of the device and showing all the internal components.

FIG. 3 is a cross sectional view of the ionization device shown in FIG. 2 and is taken along 33 of that figure.

FIG. 4 is a graph showing the relationship between the voltage applied to the diode electrodes and the current which passes through the device.

FIG. 5 is a graph showing the relationship between the shield position and the saturation current passing through the diode.

FIG. 6 is a development view of one form of serrated edge which can be applied to one end of the shield.

FIG. 7 is a view similar to FIG. 6 but showing another form of serrated edge which can be used for changing the current characteristic.

Referring now to FIGS. 1, 2, and 3, the device includes an envelope having a hollow cylindrical barrel 10 and two generally fiat end portions 11 and 12 which seal the envelope from the outside atmosphere. End 11 is sealed to the barrel 10 at its outer edge and contains a female screw portion at its center for engaging an adjusting screw 13. The adjusting screw 13 is secured to some means for indicating the internal position of a hollow shield 14. This indicating means includes a disk 15 secured to the end of the adjusting screw and a barrel portion 16 which encloses a portion of the envelope 10. FIG. 1 shows a plurality of measuring lines 17 on the rotatable barrel 16 and other lines 18 on barrel 10. This combination of indicating lines is old in the art but is very effective and useful in accurately determining the relative position of the adjusting screw and the barrel 10.

End portion 12 is composed of an insulator disk 20 which may be glass or ceramic and is sealed to the barrel 10 at its outer edge. At the center of this disk a metal insert 21 is sealed and this insert in turn is sealed to an anode electrode 22 which may be hollow for exhausting and filling the envelope with the desired ionizable gas at reduced pressure. If the filling operation uses the hollow portion of the anode a compression seal 23 is employed at the end of the sealing operation and an anode cap 24 may be used to cover the seal and provide one terminal for connection to external circuits.

On the inside of the barrel 10 a plurality of bands 25 are secured. These bands contain a substance, such as a salt of radium or americium, which emits ionizing radiation which may be either alpha, beta, or gamma radiation. It has been found convenient to first spread the ionizing substance on gold foil and then cut this foil into strips and secure it to the inside surface of the barrel with the ionizing substance between the foil and the barrel. This means of installing the radiation material is safe to use and produces a measured amount of ionizing radiation since each area of foil material may be tested in advance to measure its ionizing properties. It will be noted that one section of the barrel surface 26 contains no foil and produces no ionizing radiation. The adjacent band 25 produces a measured amount of ionization which may be characterized by the numeral 1. The band adjacent to this, 25A, may be given 10 times the ionizing properties and therefore may be characterized by the numeral 10. The third band, 25B, may have times the ionizing properties of the first band and is thus characterized by the numeral 100.

Shield 14 is secured to a metal disk 27 which includes a bearing portion 28 for supporting the inner end of the adjustable screw 13. The outer edge of disk 27 is sealed to shield 14 and to one end of a flexible bellows 30 the other end of which is sealed to end portion 11. This bellows permits movement of the shield under control of screw 13 while at the same time sealing the inside of the envelope from any leakage which might occur through the screw portion meshing with its nut.

and since there are only a certain number of ionized molecules available an increase in voltage cannot produce more current. This portion of the characteristic is termed the saturation region and is shown in FIG. 4 by line 32. If the applied voltage is increased above 1000 volts, the speed of the ionized molecules becomes great enough to cause secondary ionization effects and the straight portion of curve 32 increases abruptly until a glow discharge is formed. It is contemplated that the present ionization device will be used with applied voltages between the range of 20 volts and 1000 volts.

The operation of this device is self evident from the the above description of the structural elements. With the shield 14 as shown in FIG. 2 moved to the left for the maximum distance there will be substantially no current possible between the anode 22 and the cathode, which is conductive barrel 10. This is because all three bands 25, 25A, and 25B, are shielded from the anode by shield 14. There will be some stray ionization effects around the edge of the shield but these effects produce very little current. As the shield is moved from the zero .position on the left to the right, a greater area of the ionizing material is uncovered so that the penetrating tion current is also linear. This characteristic is illustrated If it is desired to produce over a wide range of current values. The adjustment can be made quickly and easily by the adjustment of a single screw.

The foregoing disclosure and drawings are merely illustrative of the principles of this invention and are not to be interpreted in a limiting sense. The only limi tations are to be determined by the scope of the appended claims.

We claim:

ll. An adjustable constant current device comprising;

an envelope enclosing an ionizablegas, an anode, a cathode surface, a plurality of annular band areas of radioactive material for ionizing the gas, and a movable shield for shielding portions of said areas to vary the intensity of gas ionization; each of said areas respectively formed with uniformly placed radioactive material, but each area dilfering from each other area in total ionizing radiation; each of said areas positioned on the inside surface of said envelope; said movable shield comprising a hollow cylinder with a serrated edge; and mechanical means for manually controlling the movement of said shield, said mechanical means including a screw mounted in an envelope wall and engaging said shield.

2. A constant current device as claimed in claim 1 wherein said screw is protected by a metallic bellows.

3. Aconstantcurrent device as claimed in claim 1 wherein said area bands of radioactive material are of substantially the same width and the serrations on'the end of said shield are formed with a depth equal to the band width. e

4. An adjustable constant current device comprising; an envelope enclosing an ionizable gas, an anode, a cathode surrounding the anode, a plurality of band areas of radioactive material for ionizing the gas, and a movable shield for progressively shielding portions of said areas to vary the intensity of gas ionization in a gradual predetermined manner, over a range of ionization values exceeding a factor of one hundred, each of said band areas respectively, adapted to deliver substantially equal amounts of radioaction per unit area, but each area differing from each other area in totalionizing radiation; said movable shield comprising a hollow cylinder with a serrated edge disposed in axial alignment with the envelope; a bellows of generally cylindrical shape having one end sealed to said shield and the other end secured to a portion of the envelope; and mechanical means for manually controlling the position of said shield, said means including a screw coupled to a shield and mounted in a portion of the envelope wall surrounded by said other end of the bellows, said screw extending external to the envelope for manual control.

5. A constant current device as claimed in claim .4 wherein the amount of radioactive material in said bands varies along the envelope length, said variation being in excess of a factor of three.

References Cited by the Examiner UNITED STATES PATENTS 2,640,953 6/53 Rossi 315- 2,696,563 12/54 Coleman 250-833 2,714,677 8/55 MacNeille 31361 GEORGE N. WESTBY, Primary Eicaminer.

R BERT SEGAL, x m ner. 

1. AN ADJUSTABLE CONSTANT CURRENT DEVICE COMPRISING; AN ENVELOPE ENCLOSING AN IONIZABLE GAS, AN ANODE, A CATHODE SURFACE, A PLURALITY OF ANNULAR BAND AREAS OF RADIOACTIVE MATERIAL FOR IONIZING THE GAS, AND A MOVABLE SHIELD FOR SHIELDING PORTIONS OF SAID AREAS TO VARY THE INTENSITY OF GAS IONIZATION; EACH OF SAID AREAS RESPECTIVELY FORMED WITH UNIFORMLY PLACED RADIOACTIVE MATERIAL, BUT EACH AREA DIFFERING FROM EACH OTHER AREA IN TOTAL IONIZING RADIATION; EACH OF SAID AREAS POSITIONED ON THE INSIDE SURFACE OF SAID ENVELOPE; SAID MOVABLE SHIELD COMPRISING A HOLLOW CYLINDER WITH A SERRATED EDGE; AND MECHANICAL MEANS FOR MANUALLY CONTROLLING THE MOVEMENT OF SAID SHIELD, SAID MECHANICAL MEANS INCLUDING A SCREW MOUNTED IN AN ENVELOPE WALL AND ENGAGING SAID SHIELD. 